The Kidney and Function of the Nephron Flashcards
What is the cortex?
Outer region of the kidney made of Bowman’s capsules, tubules and blood vessels.
What is the medulla?
Darker, inner region of the kidney made from loops of Henle, collecting ducts and blood vessels.
What is the pelvis?
A cavity within the kidney where urine starts to collect.
What is the ureter?
A tube that carries urine from the kidney to the bladder.
What is Bowman’s capsule?
The structure found at one end of the nephron that contains the glomerulus.
What type of cells line the inside of Bowman’s capsule?
Podocytes
What is the proximal convoluted tubule?
A tubule that connects the glomerulus to the loop of Henle.
What is the loop of Henle?
A loop that extends from the cortex, through the medulla, and back into the cortex again.
What is the distal convoluted tubule?
The tubule closest to the collecting duct
What is the collecting duct?
The tube from which many nephrons are connected to, which transports urine into the pelvis.
Where is the afferent arteriole and what does it do?
Supplies the nephron with blood and its capillaries extend into the glomerulus.
Where is the efferent arteriole and what does it do?
Leaves Bowman’s capsule and supplies the loop of Henle with blood
Name the 4 stages of osmoregulation.
Formation of glomerular filtrate
Reabsorption by the proximal convoluted tubule
Maintenance of ion gradient by loop of Henle
Reabsorption of water by distal convoluted tubule
Describe the structure of glomerular capillaries.
Endothelial cells with pores between them so substances can leak out
Why does hydrostatic pressure build in the glomerulus?
How does this lead to formation of filtrate?
Diameter of afferent arteriole greater then efferent arteriole.
This causes glomerular filtrate to squeeze out between pores in capillaries.
What makes up glomerular filtrate?
Water, ions, glucose
Why are blood cells and proteins not squeezed out of capillaries during the formation of glomerular filtrate?
They are too large
Why do epithelial cells in the proximal convoluted tubule have microvilli?
Large SA for reabsorption from filtrate
Why do epithelial cells in the proximal convoluted tubule have infoldings in their bases?
To increase SA so reabsorbed substances can be transferred to capillaries
Why do epithelial cells in the proximal convoluted tubule have high numbers of mitochondria?
To produce ATP for active transport
Name the ion actively transported out of cells lining the proximal convoluted tubule.
Is the conc of this ion now higher or lower in these cells?
Na+ actively transported out.
Na+ conc lower inside cells lining proximal convoluted tubule.
Na+ leaves the lumen of the proximal convoluted tubule by what transport process?
Where do the Na+ ions end up?
Na+ leaves the lumen by facilitated diffusion in carrier proteins and ends up in the epithelial cells lining the tubule.
Explain how cotransport of glucose/amino acids is involved in reabsorption in proximal convoluted tubule.
Facilitated diffusion of Na+ often happens alongside glucose or amino acids, so glucose/amino acids also enter cells lining the proximal convoluted tubule.
Explain how glucose/amino acids are absorbed into the blood during reabsorption from proximal convoluted tubule.
Once they have co transported into epithelial cells lining the proximal convoluted tubule, they diffuse into the blood.
What is the main responsibility of the loop of Henle?
Absorbs water from the collecting duct, concentrating urine and ensuring it has a lower water potential than the blood.
Describe the structure and permeability of the descending limb of the loop of Henle.
Thin narrow walled. Highly permeable to water, impermeable to salts .
Describe the structure and permeability of the ascending limb of the loop of Henle.
Wider and thicker walls. Walls impermeable to water but permeable to ions.
Why does water leave the descending limb by osmosis?
Where does this water go?
Because walls are highly permeable to water.
Water then enters capillaries
As you go down the descending limb, how does water potential of filtrate change?
Water potential decreases, leaving the filtrate highly concentrated.
Whereabouts in the loop of Henle will water potential be at its lowest?
At the tip
As water leaves the descending limb the loop of Henle, how does the water potential of the medulla compare to the water potential of the descending limb?
Water potential of medulla higher than in descending limb.
At the base of the ascending limb, where do sodium ions start to move and by what transport process?
Na+ ions leave the ascending limb by diffusion as the filtrate is highly concentrated.
As you go up the ascending limb, sodium ions to leave the filtrate by what transport process and how does this change the water potential of the filtrate?
Sodium ions leave by active transport and water potential of filtrate raises.
Describe the water potential gradient between the cortex and medulla between the ascending limb and collecting duct.
Water potential is higher in the cortex and lower in the medulla.
As the filtrate reaches the collecting duct, water starts to leave by osmosis - where does it go?
How does this change water potential of the filtrate?
Water passes into surrounding capillaries.
This lowers water potential of the filtrate.
Why do cells in the distal convoluted tubule contain microvilli and lots of mitochondria?
Microvilli maximise surface area.
Mitochondria produce ATP for active transport
What does the distal convoluted tubule do for reabsorption?
Makes final adjustments to water/salts absorbed and controls blood pH by selecting the ions reabsorbed.
